The expression of truth is simplicity.

When somebody genuinely understands a thing, they can say it plainly. Complicated language is occasionally necessary and far more often a symptom: either the speaker has not finished thinking, or they would rather you did not follow closely. Both look identical from outside, which is why the reasonable response to an impenetrable explanation is to ask for a simpler one rather than to assume you are the slow party.

Test your own thinking by explaining it to someone with no background. Where you reach for jargon, stop and find the plain version. The places you cannot are the places you do not yet understand.